Thermally responsive sights



Oct. 18, 1966 p v, CHOATE ET AL 3,279,072

THERMALLY RESPONSIVE SIGHTS Original Filed May 17, 1962 5 Sheets-Sheet 1 INVENTORS PAULV CHOATE ALTON F. CARR ATTORN Y Oct. 18, 1966 p, v, CHOATE ETAL 3,279,072

THERMALLY RESPONSIVE SIGHTS 5 Shets-Sheet 2 Original Filed May 17, 1962 INVENTORS Iii ATTORNEY Oct. 18, 1966 CHQATE ET AL 3,279,072

THERMALLY RESPONSIVE SIGHTS 5 Sheets-Sheet 5 Original Filed May 17, 1962 INVENTORS PAUL V CHOATE BY ALTON F CARR FIG.6

3,279,072 THERMALLY RESPONSIVE SIGHTS Paul V. Choate, Milton, and Alton F. Carr, Woburn, Mass., assignors to Norris Thermador Corporation, Los Angeles, Calif., a corporation of California Continuation of application Ser. No. 195,463, May 17, 1962. This application Apr. 12, 1965, Ser. No. 449,927 16 Claims. (Cl. 33-47) The present invention relates to sights for weapons and particularly to those for launchers for rockets utilizing solid propellants and is a continuation of our copending application Serial No. 195,463, filed May 17, 1962 now abandoned.

While it is well known that such weapons as firearms and rocket launchers much have sights that are adjustable to enable targets at different distances to be hit, such sights usually being also adjustable to compensate for the effects of wind on the projectile, the effects of heat have not been the object of much concern. This is true even though it is recognized that a firearm sighted in with a hot barrel, for example, may prove to be inaccurate when the barrel is cold.

With the use of solid propellants for rockets, it was observed that markedly different results followed any substantial temperature change. The results were that, as the temperature of the propellant decreased, the range of a rocket using that propellant was shortened with reference to a pre-selected normal while, as the temperature of that propellant increased, the rockets range was extended relative thereto. In short, the effects of temperature changes are relatively the same, .as far as sighting requirements, as changes in the distance to a target but are not as readily discerned.

As a consequence, there is a real demand to have sighting corrections made automatically in response to temperature changes and, in accordance with the invention such corrections are effected by means of a sight member that is raised or lowered by thermally responsive means in a predetermined direction and to a predetermined extent dependent on the temperature to which the element is subjected. While other types of thermally responsive means may be used, those that use bi-metallic elements are preferred because of their ruggedness, simplicity and low cost. With a weapon having both front and rear sights, the sight member, if the rear sight, must raise on a drop of temperature, or, under these conditions, a front sight must be lowered. In the case of a rise in temperature, the rear sight must be lowered or the front sight elevated. A telescopic sight presents a situation similar to a rear sight.

While the actuation of a sight by thermally responsive means must be in a predetermined relationship to the performance characteristics of the propellant, there is the added necessity that the sight must have its thermally responsive means shielded against being heated or cooled at a rate materially faster or slower than the propellant to avoid-over or under corrections, either of which would result in inaccurate sighting.

As it is desirable to have the thermally responsive means below the sight member and as the thermally responsive means must be operative or so connected to the sight members as to cause movement in a range-increasing direction as the temperature drops and vice versa, it is required, in the case of a rear sight, for example, either that the thermally responsive means contract in response to increased temperature or that the connection between the thermally responsive means and the sight member produce movement in the same direction as such contracting thermally responsive means.

In the accompanying drawings, there are shown illus- 3,279,072 Patented Oct. 18, 1966 trative embodiments of the invention from which these and other of its objectives, novel features, and advantages will be readily apparent.

In the drawings:

FIGURE 1 is a diagrammatic view illustrating sighting requirements where the efliciency of a rocket propellant decreases with a decrease in temperature,

FIGURE 2 is a rear perspective view of a rear sight in accordance with the invention,

FIGURE 3 is a section, on an increased scale, taken approximately along the indicated lines 3-3 of FIG- URE 2,

FIGURE 4 is a side elevation, on a further increased scale, of the thermally responsive means of the sight shown in FIGURES 2 and 3,

FIGURE 5 is a fragmentary elevation, on a further increase of scale, of the material of which the thermally responsive means, shown in FIGURES 3 and 4, is formed,

FIGURE 6 is a section similar to FIGURE 3 illustrating an embodiment of the invention in which the thermally responsive means is in the form of a bi-metallic coil, and

FIGURE 7 is a similar section illustrating another embodiment wherein the thermally responsive means is a U-shaped bi-metallic element.

Reference is first made to the fact that the propellant for rockets to be launched from shoulder-supported launchers is of solid form and usually in the form of sticks, with mono-perforated sticks being most commonly used. The efficiency of such a propellant is a function of its temperature at the time it is ignited with the efliciency improving as the temperature rises and vice versa.

In FIGURE 1, a launcher is generally indicated at 10 and the path of its rocket 11 to the target 12 is indicated at N. The launcher 10 is shown as having a front sight 13, and a rear sight 14. While any type of front sight may be used, the front sight 13 is of a transparent plastic having sighting indicia thereon as is fully detailed in the co-pending application of Paul V. Choate and Charles B. Weeks, Serial No. 151,894, filed November 13, 1961, now United States Patent No. 3,122,059. It is, of course, conventional for sighting arrangements to be adjustable to enable corrections to be made for different distances and wind factors and the means for so doing are not herein shown as they form no part of the present invention. It is assumed that the sights of the launcher 10 are set with the path N being normal for the rocket 11 when the temperature of its propellant, just prior to being ignited, is in the order of say, 70 F.

As the temperature drops, the efliciency of the propellant decreases so that the path of the rocket, when the temperature of its propellant is at some temperature lower than 70 F., is indicated at C and passes below the target 12. As in the case of an increased range, it is now necessary to make correction by raising the muzzle of the launcher 10 as by raising the rear sight 14. As the temperature rises above the assumed temperature for which the path N is normal, the efficiency of the propellant increases so that the path N of the rocket, when ignited with its propellant at that elevated temperature passes above the target 12. As in the case of a shorter range, it is now necessary to make corrections by lowering the muzzle of the rocket as by lowering the rear sight 14.

In accordance with the invention, the sight corrections are made automatically so that variations in propellant eificiency do not need to be considered in firing.

Referring now to FIGURE 2, it will be seen that the rear sight 14 consists of a mount 15 having its lower end forked as at 16 with the ends having aligned apertures 17 for the transverse attaching pivot not shown. The mount 15 has an upwardly disposed, cylindrical chamber 18 opening between the forked ends of the mount and in communication with a transverse, vertical slot 19 intersected by a fore and aft passage 20 provided with windows 21 and establishing the sight axis. It is preferred that the windows 21 protrude slightly for ease in cleaning them.

The sight member is shown as being in the form of a blade 22 having a peep aperture 23 and slidably guided in the slot 19 with its lower end connected to thermally responsive means in the form of a helical element 24 formed from bi-metallic stock 25 which is itself in the form of a helix, as may best be seen in FIGURE 4, and is of the type contracting in response to temperature rises.

The element 24 is a free fit in an insulating sleeve 26, typically aluminum, fitted within the cylindrical chamber 18. The lower end of the element 24 extends freely through a central hole in a disc 27 and is attached to a loose anchor 28 to prevent binding as the coil expands and contracts. A cap 29 is sealed in the exposed end of the chamber 18.

In FIGURE 6, there is shown another embodiment of the invention and, for convenience, the same mount construction is used. Like parts are distinguished from those of the embodiment just described by the sufiix letter A. It will be noted that the blade 22A is provided with a depending leg 30 having a notch 31 in which is caught the free end 32 of a thermally responsive element in the form of a coil 33 of bi-metallic stock. The coil 33 has its other end secured to a cross bar 34 fastened to the interior of the shell 26A so that the blade 22A is moved downwardly as the temperature increases and upwardly as the temperature drops.

Similarly, the embodiment of the invention illustrated by FIGURE 7 is shown as employing the same type of mount as has been described. Like parts are distinguished from those of the other embodiments by the suffix B. In the embodiment of FIGURE 7, the blade 22B has a diagonally disposed slot 35 through which extends a pin 36 at the upper end of a fork 37. The lower end of the fork 37 is secured to the free end 38 of a thermally responsive element 39 of bi-metallic stock and approximately U-shaped with its yoke-carrying end moving away from its anchored end as the temperature drops. With a like element but having its yoke-carrying end moving in the opposite direction as the temperature drops, the slot 35 would be inclined in a direction opposite to that shown. As with the other embodiments of the invention, the blade 22B is pulled downwardly as the temperature rises and is elevated as the temperature drops.

With sights of the types disclosed, the blades move up and down in response to temperature changes. In practice, these movements are accurately correlated to the characteristics of the propellant as determined by temperature. It will be apparent that as the propellant is within the rocket and the rocket is within the launcher while the sight is exposed, the thermally responsive means must be prevented from too promptly registering temperature changes and the aluminum sleeve is a simple and inexpensive means for so doing. Other types of insulating the thermally responsive means may, of course, be used.

From the foregoing it will be apparent that the invention makes possible sights which accurately adjust themselves to temperature changes in relation to the eifect such changes have on accuracy.

We claim:

1. A sight comprising a mount, a sighting unit attached to said mount and including a vertically movable sight member and thermally responsive means connected thereto to cause the vertical position of said member relative to said mount to vary in a predetermined direction and to a predetermined extent dependent on the temperature to which said means is subjected, in a range-increasing direction when said temperature is falling and in a rangedecreasing direction when said temperature is rising.

2. A sight comprising a mount, a sighting unit attached to said mount and including a vertically movable sight member and thermally responsive means connected thereto to cause the vertical position of said member relative to said mount to vary in a predetermined direction and to a predetermined extent dependent on the temperature to which said means is subjected and means insulating said thermally responsive means against the direct transfer of heat thereto, in a range-increasing direction when said temperature is falling and in a range-decreasing direction when said temperature is rising.

3. A sight comprising a mount, a sighting unit attached to said mount and including a vertically movable sight member and thermally responsive means connected thereto to cause the vertical position of said member relative to said mount to vary in a predetermined direction and to a predetermined extent dependent on the temperature to which said means is subjected, and heat reflecting means shielding said thermally responsive means against the direct transfer of heat thereto, in a range-increasing direction when said temperature is falling and in a rangedecreasing direction when said temperature is rising.

4. A sight comprising a mount, a sighting unit attached to said mount and including a vertically movable sight member and thermally responsive means connected thereto to cause the vertical position of said member relative to said mount to vary in a predetermined direction and to a predetermined extent dependent on the temperature to which said means is subjected, said thermally responsive means being below said member and contracting as its temperature rises.

5. The sight of claim 4 in which the thermally responsive means is in the form of a helical element of stock which is a bi-metallic helix.

6. A sight comprising a mount, a sighting unit attached to said mount and including a vertically movable sight member and thermally responsive means below said member and expanding as its temperature rises, and a connection between said means and said member to cause predetermined downward movement of said member relative to said mount as the temperature rises and predetermined upward movement thereof as the temperature falls.

7. The sight of claim 6 in which the thermally responsive means is a U-shaped, bi-metallic element.

8. The sight of claim 6 in which the thermally responsive means is a bi-metallic element in the form of a coil.

9. A sight comprising a mount having a chamber, thermally responsive means mounted in said chamber, and a sight member connected to said means and slidably connected to said mount to move vertically relative thereto in a range-increasing direction when the temperature is falling and in a range-decreasing direction when the temperature is rising.

10. A sight comprising a mount having a chamber including a portion having a vertical guide slot, thermally responsive means mounted in said chamber, and a sight member slidable in said guide slot and connected to said means to move vertically relative to said portion in a range-increasing direction when the temperature is falling and in a range-decreasing direction when the temperature is rising.

11. A sight comprising a mount having a chamber provided with alined windows defining a sight axis, thermally responsive means in said chamber, and a sight member connected to said means and exposed in said axis, said member being movable in said chamber vertically with respect to said axis.

12. A sight comprising a mount having a chamber provided with alined Windows defining a sight axis, thermally responsive means in said chamber, a sight member connected to said means and exposed in said axis, said member being movable in said chamber vertically with respect to said axis, and heat reflecting shield within said chamber housing said thermally responsive means.

13. A sight comprising a mount having a chamber including a lower portion and an upper portion having a vertical guide slot, said chamber provided with alined windows defining a sight axis at right angles to the plane of said slot, thermally responsive means in said chamber in the form of a helical element each turn of which is a bi-metallic helix and contracting on the application of heat thereto, one end of said element being anchored in said chamber a sight member connected to the other end of said element Within said chamber and exposed in said axis, said member being slidable in said guide slot, and an insulating sleeve in said cylindrical portion surrounding said element.

14. A sight comprising a mount having a chamber including a lower portion and an upper portion having a vertical guide slot, said chamber provided with alined windows defining a sight axis at right angles to the plane of said slot, thermally responsive means in said chamber in the form of a U-shaped element of a bi-metallic stock and expanding on the application of heat thereto, one end of said element being anchored in said chamber a sight member slidable in said guide slot and exposed in said axis, an insulating sleeve in said lower portion surrounding said element, said sight member including an end extending into said chamber and having a diagonal slot, and the other arms of said element including a stud slidable in said slot and operable, as it slides, to move said sight member in a vertical direction.

15. A sight comprising a mount having a chamber including a lower portion and an upper portion having a vertical guide slot, said chamber provided with alined windows defining a sight axis at right angles to the plane of said slot, thermally responsive means in said chamher in the form of a coil of stock which is bi-metallic and expanding on the application of heat thereto, a one end of said coil being anchored in said chamber, sight member slidable in said guide slot and exposed in said axis, an insulating sleeve in said lower portion surrounding said element, and the free end of said coil being connected to said sight member.

16. A sight comprising a mount having a chamber provided with alined windows defining a sight axis, thermally responsive means in said chamber, a sight member within said chamber between and blocking said windows and connected to said means, said sight member being movably supported by said mount for movement vertically with respect to said axis, said sight member having an aperture, said windows being in the form of vertical slots of a width substantially greater than the diameter of said sight member aperture and of such length that said aperture is exposed in any position of said sight member.

References Cited by the Examiner UNITED STATES PATENTS 1,138,687 5/1915 Reichmann 177-226 2,353,155 7/1944 Hal-l 73-362 2,608,862 9/1952 Miller 73-3639 FOREIGN PATENTS 815,048 4/1937 France.

LEONARD FORMAN, Primary Examiner.

ISAAC LISANN, Examiner.

J. D. BOOS, Assistant Examiner. 

1. A SIGHT COMPRISING A MOUNT, A SIGHTING UNIT ATTACHED TO SAID MOUNT AND INCLUDING A VERTICALLY MOVABLE SIGHT MEMBER AND THERMALLY RESPONSIVE MEANS CONNECTED THERETO TO CAUSE THE VERTICAL POSITION OF SAID MEMBER RELATIVE TO SAID AMOUNT TO VARY IN A PREDETERMINED DIRECTION AND 